Question

if the sum of first k terms is 3ksq.- k and the common difference is 6 . find tits first term​

Answer 1

Answer: a = 2

Explanation:

taking k = n

sₙ = 3n² - n

so s₁ = 3(1)² - 1

       = 3 -1

       = 2

and s₁ = a₁

therefore a = 2

Answer 2

Answer:

I have attached the solution in the image.. hope this helps u

I do not see how the common difference is required here though..